Add button to message template

Signed-off-by: Émile Ré <nemile.re@gmail.com>

pkg/trust/templates/access-request.json.tmpl

@@ -30,6 +30,16 @@
           "value": "{{.SlackMessageID}}",
           "style": "primary"
         },
+        {
+          "type": "button",
+          "text": {
+            "type": "plain_text",
+            "text": "❌ Reject All"
+          },
+          "action_id": "reject_all",
+          "value": "{{.SlackMessageID}}",
+          "style": "danger"
+        },
         {
           "type": "button",
           "text": {